Language statistics bar for repositories (#8037)

* Implementation for calculating language statistics

Impement saving code language statistics to database

Implement rendering langauge stats

Add primary laguage to show in repository list

Implement repository stats indexer queue

Add indexer test

Refactor to use queue module

* Do not timeout for queues

modules/indexer/stats/indexer.go

@@ -0,0 +1,85 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package stats
+
+import (
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/graceful"
+	"code.gitea.io/gitea/modules/log"
+)
+
+// Indexer defines an interface to index repository stats
+type Indexer interface {
+	Index(id int64) error
+	Close()
+}
+
+// indexer represents a indexer instance
+var indexer Indexer
+
+// Init initialize the repo indexer
+func Init() error {
+	indexer = &DBIndexer{}
+
+	if err := initStatsQueue(); err != nil {
+		return err
+	}
+
+	go populateRepoIndexer()
+
+	return nil
+}
+
+// populateRepoIndexer populate the repo indexer with pre-existing data. This
+// should only be run when the indexer is created for the first time.
+func populateRepoIndexer() {
+	log.Info("Populating the repo stats indexer with existing repositories")
+
+	isShutdown := graceful.GetManager().IsShutdown()
+
+	exist, err := models.IsTableNotEmpty("repository")
+	if err != nil {
+		log.Fatal("System error: %v", err)
+	} else if !exist {
+		return
+	}
+
+	var maxRepoID int64
+	if maxRepoID, err = models.GetMaxID("repository"); err != nil {
+		log.Fatal("System error: %v", err)
+	}
+
+	// start with the maximum existing repo ID and work backwards, so that we
+	// don't include repos that are created after gitea starts; such repos will
+	// already be added to the indexer, and we don't need to add them again.
+	for maxRepoID > 0 {
+		select {
+		case <-isShutdown:
+			log.Info("Repository Stats Indexer population shutdown before completion")
+			return
+		default:
+		}
+		ids, err := models.GetUnindexedRepos(models.RepoIndexerTypeStats, maxRepoID, 0, 50)
+		if err != nil {
+			log.Error("populateRepoIndexer: %v", err)
+			return
+		} else if len(ids) == 0 {
+			break
+		}
+		for _, id := range ids {
+			select {
+			case <-isShutdown:
+				log.Info("Repository Stats Indexer population shutdown before completion")
+				return
+			default:
+			}
+			if err := statsQueue.Push(id); err != nil {
+				log.Error("statsQueue.Push: %v", err)
+			}
+			maxRepoID = id - 1
+		}
+	}
+	log.Info("Done (re)populating the repo stats indexer with existing repositories")
+}